1. Field of the Invention
This invention relates to appparatus for transporting and aligning silicon wafers or the like and methods of using such apparatus.
2. Introduction to the Invention
In the manufacture of solid state devices, silicon wafers are moved between different work stations, usually in cassettes which hold a number of wafers stacked one above the other in horizontal pockets, each pocket formed of a generally U-shaped groove into which the wafer can be placed. Careful handling of the wafers is essential.
It is now often preferred that neither face of the wafer makes contact with the handling device; also, many processes require that the wafer has a known orientation with respect to a flat or notch on the perimeter of the wafer that defines its crystaline plane.
Manually operated devices are presently available and in use that can align the flats or notches on wafers while in their cassettes to approximately the same orientation. It is required that such approximate prealignment is used in the preferred embodiment of this invention.
No currently used wafer transport or alignment device was found to have the same attributes as those described by this invention.
This invention provides a means for simultaneously precisely aligning `approximately prealigned` wafers, with either flats or notches, during transportion from the cassette to another defined location, without touching either face of the wafer. It is also shown how, with an optional motor fitted, the device can precisely align randomly oriented wafers and lastly how the device can be incorporated into a multiple cassette, high throughput production machine facilitating continuous automatic operation.